NEWTOWN, Conn. — Investigators seized cellphones, computers and computer games during a search of mass murderer Adam Lanza's home — but found no evidence that he was being treated with any drugs prescribed for mental illness, a source told Hearst Connecticut Newspapers.

Investigators are now using search warrants to get medical records to determine if Lanza was being treated for a medical or psychiatric ailment, and what — if anything — was prescribed, the source said. Lanza's parents had told friends and divorce mediators that he had Asperger's syndrome, a form of high-functioning autism, but it's unclear if he had ever been formally diagnosed.

All this could be critical in determining what caused Lanza shoot four bullets into his mother, Nancy Lanza, 52, who sources said was found dead in bed.

Detectives are poring through cellphone records and voicemails, viewing text messages and social network pages and analyzing computer equipment seized from his mother's upscale home — hoping to find answers.

Investigators have not managed to retrieve any data from a computer they took from Adam Lanza's home because he had all but destroyed the hard drive, a senior law enforcement official said Monday.

Hearing approaching police smash windows at they began entering the school, Lanza sought cover in another room and shot himself in the head — just about four minutes after his rampage began.

"It could have been a lot worse," said a second source who was at the scene Friday. "He still had hundreds of more rounds. I'm convinced he would have continued going from classroom to classroom. He only killed himself because he heard the police arrive."

"They are looking at everything," said Robert Paquette, a former FBI agent. "They poring over anything and everything. Was he on meds? ... How was his relationship with his mother? What video games did he play? How often did he play? Where did he learn to shoot? ... What they want to determine is why?""